This invention pertains to pristine phenylpropylalkylsiloxanes and a method for their preparation. The pristine phenylpropylalkylsiloxanes of the instant invention contain no detectable silicon hydride (--SiH), free organics (--C.dbd.--) or free inorganics. Additionally, the pristine phenylpropylalkylsiloxanes of the instant invention are high refractive index organosilicone polymers.
Silicone polymers which have high refractive indices, dimethylsilicone-like sensory properties, organic compatibility and high tolerance to strong acid media are desired in the art. Dimethylsilicone fluids typically have refractive indices of approximately 1.4 regardless of the structure or molecular weight of the fluid. Although some alkylmethylsilicones have improved organic compatibility as well as dimethylsilicone-like sensory properties, they generally do not have refractive indices greater than about 1.45. Further, the alkylmethylsilicones that have a refractive index that high are generally waxes. Phenyl containing silicones can provide the desired refractive index since the refractive index can be correlated to the amount of phenyl substitution relative to methyl substitution. However, phenyl-containing polymers where the phenyl is directly bonded to the silicone have a low tolerance to acid media and are costly to produce. This limits the applications in which these phenyl-containing polymer can be used. It has been found that pristine phenylpropylalkylsiloxanes of the instant invention can provide the desired properties.
When 2-phenylpropylalkylsiloxanes are produced by the standard hydrosilylation route wherein .alpha.-methylstyrene is reacted with a --SiH containing organopolysiloxane several difficulties are encountered which prohibit the production of low cost, pristine phenylpropylalkylsiloxanes. The first problem is that when the reaction is run with a slight excess of alphamethylstyrene and less than 150 ppm platinum the reaction does not go to completion resulting in phenylpropylalkylsiloxanes that contain silicon hydride (--SiH). At higher concentrations of platinum the reaction goes to completion (no detectable --SiH) but the resulting product has an undesirable color and odor. Further, use of higher amounts of platinum make the product costly to produce.
Disclosed in "Addition of Silicon Hydrides to Olefinic Double Bonds. IV. The Addition to Styrene and .alpha.-Methylstyrene" by J. Speier and J. Ryan, Journal of Organic Chemistry, 24, 2052(1959), is a method for making phenylpropylalkyl hydrolysates as an intermediate in the production of phenylpropylalkyl cyclosiloxanes. The method disclosed in Speier and Ryan consists of producing distilled phenylpropylmethyldichlorosilane. The distilled phenylpropylmethyldichlorosilane is then hydrolyzed and the cyclosiloxanes are recovered by distillation. Speier and Ryan does not disclose a process for producing pristine phenylpropylalkylsiloxanes.
U.S. Pat. No. 3,088,964 to Ryan discloses several methods for producing phenylpropylmethylsiloxanes. The first method comprises hydrolyzing phenylpropylmethyldichlorosilane. The hydrolyzate is then cracked with a basic catalyst to produce phenylpropylmethylcyclosiloxanes. Another method comprises reacting .alpha.-methylstyrene with an organosiloxane containing --SiH atoms. Neither of the methods disclosed in U.S. Pat. No. 3,088,964 are capable of producing pristine phenylpropylalkylsiloxanes.
U.S. Pat. No. 3,186,944 to Kookootsedes and Speier discloses the use of 2-phenylpropylmethylsiloxane, ethylmethylsiloxane or propylmethylsiloxane copolymers as mold release agents. These copolymers may be prepared by hydrosilylation of .alpha.-methylstyrene with an excess of methylhydrogen siloxane followed by hydrosilylation with an excess of propylene or ethylene. Another method comprises hydrosilylation of .alpha.-methylstyrene with methylhydrogen siloxane and thereafter copolymerizing with ethylmethylsiloxane or propylmethylsiloxane. A third method comprises cohydrolyzing phenylpropyl and ethyl or propyl methyldichlorosilanes. None of these methods are capable of producing pristine phenylpropylalkylsiloxanes.
U.S. Pat. No. 3,221,040 to Pater discloses several methods for making copolymeric organosilicon lubricants. Pater discloses that the lubricants can be produced by (1) equilibration of cyclosiloxanes, hexahydrocarbyldisiloxane and tetra(phenylethyl)tetramethylcyclotetrasiloxane in an acidic or basic medium or (2) cohydrolysis and co-condensation of the corresponding chlorosilanes. Pater does not disclose methods for making pristine phenylpropylalkylsiloxanes.
Finally, U.S. Pat. No. 3,839,384 to Morehouse discloses a high resilience polyether urethane foam which contains a minor amount of an aralkyl modified siloxane. The aralkyl modified siloxanes can be produced by the method disclosed in U.S. Pat. No. 3,221,040 discussed above. Morehouse does not disclose pristine phenylpropylalkylsiloxanes or methods for making the same.
It is an object of the instant invention to provide pristine phenylpropylalkylsiloxanes which contain no detectable silicon hydride (--SiH), free organics (--C.dbd.--) or free inorganics and are colorless and odorless.
It is further an object of the instant invention to provide a method for the preparation of the pristine phenylpropylalkylsiloxanes which allows for the production of pristine phenylpropylalkylsiloxanes having varying refractive indices.